『Abstract
　A sequential five-step extraction scheme for phosphorus pools in freshwater sediment was modified for use in marine sediments. In the second step phosphate bound to reducible forms of iron and manganese (‘iron-bound P’) is extracted by a bicarbonate buffered dithionite solution (BD-reagent). The extraction scheme was tested on sediment from 16 m water depth in Aarhus Bay, DK and used in two other marine sediments: Kattegat at 56 m and Skagerrak at 695 m depth. By comparing the BD-extractable P-pool with both the pool of iron in the BD-fraction and the pool of oxidized, amorphous or poorly crystalline iron (am.FeOOH), highly significant correlations (p＜0.001) were observed in all three sediments. Thus, we conclude that the BD-reagent was very specific for iron-bound P. Further evidence for this came from two experiments: 1) Enhanced BD treatment did not result in additional phosphate extraction and 2) by sequential extraction of phosphorus pools in pure cultures of diatoms and cyanobacteria no phosphate was recovered in the BD-fraction. The pool of am.FeOOH was very important for controlling porewater phosphate concentration which was inferred from the significant inverse relationships between the two parameters (p＜0.001) in all sediments studied. Further, an isotopic exchange experiment with ³²PO4^3- revealed that BD-extractable P was by far the most exchangeable P-pool even deep in the sediment where the pool size was small. Iron-bound P made up 33-45％ of total P in the surface sediments. The ratio between iron-bound phosphate and am.FeOOH was 8-11 in Aarhus Bay and Kattegat. In Skagerrak the ratio was 17, which may indicate that the iron mineral extracted from this sediment is less capable of adsorbing phosphate or less saturated with phosphate.』

Introduction
Study site
Methods
　Sediment sampling
　Sequential extraction of phosphorus pools
　Analysis of phosphorus
　Extraction of am.FeOOH
　Statistics
Results
　Control experiments
　Results from the three stations
Discussion
Acknowledgements
References

図1．海洋堆積物中のリン・プールに対する連続抽出法の図示．略号；TP（全リン、total P）、SRP（可溶の反応性リン、soluble reactive P）、NRP（非反応性リン、non-reactive P）、BD（炭酸水素塩−亜ジチオン酸、bicarbonate-dithionite）．（元は図）

〔淡水堆積物の抽出法はPsenner et al.（1988）による。〕

ステップ	処理		リン画分	その他
1gの湿った堆積物試料
１	250 mlの0.46M NaCl、1時間、 上澄み液⇒	1.00 mlの1M H2SO4（硫酸）、 51 mlのNaCl画分⇒	TPNaCl、SRPNaCl	NRPNaCl＝TPNaCl−SRPNaCl
	25.0 mlの0.46M NaCl、 上澄み液⇒
２	25 mlのBD、1時間、 上澄み液⇒	8.00 mlの1M H2SO4（硫酸）、 106 mlのBD画分⇒	曝気1時間、 FeBD、MnBD、 SRPBD⇒	発色錯体の抽出 ヘキサノール／イソプロパノール（hexanol/isopropanol）
	25 mlのBD、 上澄み液⇒
	25 mlのBD、 上澄み液⇒
	25.0 mlの0.46M NaCl、 上澄み液⇒
３	25.0 mlの0.1M NaOH（水酸化ナトリウム）、18時間、 上澄み液⇒	8.00 mlの1M H2SO4（硫酸）、 78 mlのNaOH画分	TPNaOH、SRPNaOH	NRPNaOH＝TPNaOH−SRPNaOH
	25.0 mlの0.1M NaOH、 上澄み液⇒
	25.0 mlの0.46M NaCl、 上澄み液⇒
４	25.0 mlの0.5M HCｌ（塩酸）、1時間、 上澄み液⇒	50 mlのHCｌ画分	SRPHCl
	25.0 mlの0.46M NaCl、 上澄み液⇒
５	堆積物残渣を105℃で乾燥、 520℃で強熱（ignition）
	25.0 mlの1M HCｌ（塩酸）、10分間沸騰、 上澄み液⇒	100.0 mlの蒸留水、 100.0 mlの残渣（residual）画分	SRPRes